This invention relates in general to xerography and more specifically to a novel photosensitive device.
In recent years, interest has been shown in flexible electrophotographic plates for use in high speed office copying machines. Some of these plates are multilayered devices comprising, a conductive substrate layer, an adhesive-blocking interface layer, a charge generation layer and a charge transport layer. The charge transport layer comprises an organic charge transport molecule dissolved in a polymeric matrix material. This layer is substantially nonabsorbing in the spectral region of intended use, i.e. visible light, but is "active" in that it allows (1) injection of photogenerated holes from the charge generation layer and (2) efficient transport of these charges to the surface of the transport layer to discharge a surface charge thereon.
Certain classes of hole transport molecules, such as the diaryl and triarylmethanes, have been extensively studied as solutions or dispersions in polycarbonate polymers. The photooxidative stability of these classes of compounds has been found to be poor. As photoreceptor devices employing these classes of compounds are subjected to ultraviolet radiation, a condition known as "cycle up" progressively develops as the device is cycled in the xerographic machines. "Cycle up" refers to the bulk trapping of holes in the transport layer and in a relatively short period of time efficient discharge of the charged surface of the photoreceptor is lost.